A fail bit map (hereinafter, simply referred to as FBM) is used in a failure analyzing method of a semiconductor memory that has plural memory cells. The FBM is used to perform an electric characteristic test with respect to all of the memory cells using a tester and display the test result at the position corresponding to each memory cell.
In the semiconductor memory according to the related art, since the memory cells are disposed on a plane, the FBM is also represented by the two-dimensional coordinates (XY coordinates), and, naturally, a failure classification of the FBM is based on an FBM of a two-dimensional coordinate system. In the failure classification of the FBM of the two-dimensional coordinate system, failures are classified into failure types that are previously defined by information of a positional relationship between the failed cells and the distribution or density of the failed cells.
For example, an independent failure of one bit where there is no failure around the independent failure is classified as “BIT.” In the case in which failures are continuous on the same X axis, the failures are classified as “WLINE.” In the case in which failures are continuous on the same Y axis, the failures are classified as “BLINE.” The other adjacent failures are classified as “OTHER.”
In order to reduce the processing time needed for the failure classification of the FBM, the number of failures in a set area is counted, and the failures are classified as “failed area” or “multiple failed bits” according to the number of failures.
In recent years, a semiconductor memory where memory cells are disposed three-dimensionally has been developed. However, in the related art, the failure classification of the FBM is based on the two-dimensional FBM. For this reason, with respect to the three-dimensional memory, the failure types cannot be classified by using the method in which the FBM is divided for each layer into the two-dimensional FBM, the failure classification of the FBM is executed and failures crossing the layers are detected.